Construction of multifunctional boron nitride nanosheet towards reducing toxic volatiles (CO and HCN) generation and fire hazard of thermoplastic polyurethane.

Considerable toxic volatiles (CO and HCN) generation and high fire hazard has definitely compromised the application of thermoplastic polyurethane (TPU). Here, a novel functionalization strategy for bulky h-BN is adopted to obtain the multifunctional CPBN, aiming at the flame retardancy reinforcement of TPU. The multifunctional CPBN is successfully prepared via the wrapping of phytic acid doped polypyrrole shell, following with the adsorption of copper ions. The obviously decreased peak heat release rate, peak smoke production rate and total smoke production values, obtained from cone test, confirms the reduced fire hazard of TPU composite with CPBN. The dramatic suppressions on CO and HCN releases can also be observed from TG-IR test. Tensile test demonstrates that adding CPBN favors the reinforcement in mechanical property of TPU. Thus, the concurrent improvements in flame retardancy and mechanical performance are achieved by incorporating CPBN. This work opens up new avenues for the functionalization of h-BN, and thus facilitates its promising applications in polymer-matrix composite.

Construction of Hierarchical Natural Fabric Surface Structure Based on Two-Dimensional Boron Nitride Nanosheets and Its Application for Preparing Biobased Toughened Unsaturated Polyester Resin Composites.

It has been a big challenge to prepare the unsaturated polyester resin (UPR) composites with good fire safety, interfacial quality, and impact strength in an environmentally friendly way. In this study, to improve interfacial performance of fabric-reinforced UPR composites, nontoxic two-dimensional hexagonal boron nitride (h-BN) nanosheets were assembled on the surface of ramie fabrics, where sodium alginate acts as a green dispersant to disperse h-BN sheets during the process. Then, the biobased phosphorus-containing toughening agent (PCTA) was synthesized to simultaneously improve the impact strength and fire safety of the composite. With application of h-BN nanosheets-assembled fabric (AF) and 20 wt % of PCTA, the AF/UPR@PCTA20 composite presented the maximum 41.2% decrease in the value of peak heat release rate and a maximum 17.8% decrease in the value of total heat release, which also reached V-0 rating in the vertical burning test. Meanwhile, the AF/UPR@PCTA20 composite showed an obvious increase in limiting oxygen index, from 24.0 to 29.5% compared with RF/UPR. The flame retardant mechanism was investigated from gas phase and condensed phase. Furthermore, compared to neat RF/UPR composite, the AF/UPR@PCTA20 composite showed a significant 68.8% improvement in impact strength, implying an extreme toughening effect of PCTA on UPR composites. The research provides a viable green method for the development of environmentally friendly UPR composites in the future.